The present invention generally relates to language conversion systems, and more particularly to an interactive language conversion system for a machine translation system.
The existing machine translation systems do not have sufficient knowledge to automatically make correct translations. Hence, interactive systems have been proposed to compensate for the lack of knowledge by making inquiries to the user.
According to the popular systems employed in the conventional machine translation systems, the original (or source) language is analyzed to obtain a result (tree structure), the original language is converted into the tree structure of the object language in parts based on this result, and the object language is generated based on this conversion. This conversion system is sometimes referred to as the forward propagation structure conversion system. In addition, various systems have been proposed which eliminate the fuzziness by making inquiries to the user in this forward propagation structure conversion system. Examples of such systems which eliminate the fuzziness are proposed in Ashizawa et al., "A Method of Presenting Case Categorial Ambiguity by Illustrative Sentences in Japanese-English Machine Translation by Monolingual Dialogue", National Conference of the 42nd Information Processing Society (First Term of 1991) and Kumano et al., "User-Cooperative Japanese Sentence Generation" National Conference of the 42nd Information Processing Society (First Term of 1991).
On the other hand, several conversion systems have been proposed which do not use an original language input in a collective form and obtain all information through inquiries to the user. An example of such a conversion system is proposed in Saito et al., "Automatically Writing a Letter in a Foreign Language", Symposium of the Natural Language Processing Technology, November 1984.
In addition, in the forward propagation structure conversion system described above, there is also a proposal to use the knowledge of the object language for the selection of the translated word. An example of such a system is proposed in H. Nomiyama, "Lexical Selection Mechanism in Machine Translation Using Target Language Knowledge", National Conference of the 42nd Information Processing Society (First Term of 1991).
Furthermore, there are proposed systems which prepare a large number of examples of translated sentences in advance, and retrieve a translation which includes an original language phrase which is closest to the original language input. In this case, only the difference between the original language input and the original language sentence within the translation is converted, and the translated sentence within the translation is modified depending on the result of the conversion.
The popular conventional system converts the analysis (tree structure) of the original language into the tree structure of the object language in parts, and generates the object language. According to this system, even if the lack of knowledge is compensated for by the interaction with the user, the system tends to take a original-language-based structure. As a result, the sentence form is unnatural for the object language, and the expression is unnatural.
On the other hand, in the system which obtains all the information through inquiries with the user, it is necessary to prepare an extremely large amount of data in order to cope with a wide range of documents. In addition, the operation is machine initiated from the beginning and makes the user feel under control of the machine.
The information required in the object language is very often missing in the sentence of the original language. For this reason, the system in which there is no interaction with the user tends to frequently generate incomplete output.
Moreover, the information necessary in the object language may not exist in the original sentence. According to the conventional system, the translation is in many cases completed by supplementing such necessary information by a default process. However, erroneous information may be added and necessary information may be dropped if the default process is insufficient, and this method tends to generate an unnatural translation.
On the other hand, according to the translation system which uses the examples of translated sentences, an extremely large amount of examples of translated sentences must be prepared in order to cope with a wide range of documents.